Bumper beam arrangement

ABSTRACT

The bumper beam  11  of a vehicle has a hat profile and it is mounted in two tapered crash boxes  12, 13 , which extend into the hat profile with their narrow ends. These narrow ends are fixed to the bottom of the hat profile so that the crash boxes will flatten out the hat profile when they are axially compressed. This arrangement is particularly advantageous for reducing the damages in low-velocity offset crashes that have an effect on only one of the crash boxes since it reduces the risk of damages on other parts than the crash box and the bumper beam.

TECHNICAL FIELD

This invention relates to a bumper beam arrangement for a vehicle,comprising a bumper beam that has an open profile with a top end and twosides, wherein the beam is mounted on two crash boxes, which protrudeinto the profile and are mounted to the top end of the profile.

DESCRIPTION OF PRIOR ART

To mount bumper beams in crash boxes is known for example fromEP-0763448 A1, DE-19537186 A1, DE-4127381 A1, and U.S. Pat. No.3,998,485 A1. The crash boxes take up energy in a crash by beingplastically deformed axially. The strength of the crash boxes can bedesigned for high-speed crashes, but crash boxes can alternatively bedesigned for low speed crashes.

U.S. Pat. No. 3,998,485 A1 shows crash boxes for low speed crashes inthe form of tubes with a constant cross section, in which a bumper beamwith a U-formed cross section is mounted. When a crash box is axiallycompressed, the two sides of the bumper beam will be forced into thebody of the vehicle and cause damages also in a crash at very low speed.In a light offset crash on one of the crash boxes, this crash box willbe axially compressed while the bumper beam will practically not bedeformed. Yet, the bumper beam will damage the vehicle body. Conicalcrash boxes are shown at the rear of the tube formed crash boxes andthese conical crash boxes are adapted not to be deformed until the tubeformed crash boxes have been compressed.

Bumper beams having hat profile are shown for example in WO-94/0770.

OBJECT OF INVENTION

It is an object of the invention to reduce the risk of damage on thebody in low velocity crashes and in particular in such offset crashes.To this end, the crash boxes taper off and protrudes into the profilewith their narrow ends so that the crash boxes force the sides of theprofile to widen the profile and make it flatter when the crash boxesare axially compressed. The invention is defined by the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of a bumper beam of a passenger vehicle, mounted tothe vehicle in accordance with the invention.

FIG. 2 is a section taken along the line 2—2 in FIG. 1 and it shows oneof two crash boxes shown in FIG. 1.

FIGS. 3-6 correspond to FIG. 2, but they are shown in various stages ofcompression of the crash box shown in FIG. 2 when the bumper beam hits abarrier.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows one end of a vehicle, for example a passenger car, whichhas a bumper beam 11 mounted in two crash boxes 12,13, which are mountedin a structural part of the vehicle body. In the figures, the crashboxes are shown mounted on the ends of the side rails (side beams) 15,16of the vehicle body. In the figure, a panel 17 is shown, which may be afront panel or a rear panel of the vehicle and such a panel has often anenlargement 18 in the middle so as to give place for a radiator or aspare wheel. The bumper beam is usually curved as shown in order to giveplace for such an enlargement 18. A non-illustrated shell of plasticsusually hides the bumper beam.

FIG. 2 is a section through the crash box 12 and the bumper beam 11 andit is taken along line 2—2 in FIG. 1. The bumper beam 11 has an openprofile shown as a hat profile with a crown comprising a top or centralflange 20 and two sides or webs 21,22 that end in two side flanges(brims) 23,24. The bumper beam 11 is mounted with its top end 20 in oneend of the crash box 12 so that the crash box extends into the bumperbeam and fills out a major part of the cross section of the bumper beam.The crash box 12 may have a round, rectangular or square cross sectionand it widens towards its mounting to the vehicle as shown so that it iswider at its base than the distance between the two sides of the bumperbeam. It has deformation guides 25.

The FIGS. 3-6 show in a sequence the compression of the crash box 12when the bumper beam hits a barrier 28. The crash box folds and thefolds forces the sides 21,22 of the bumper beam outwards so that thebumper beam flattens out. Therefore, the sides of the bumper beam willnot hit the panel 17. In low velocity crashes and in particular in lowvelocity off-set crashes on only one of the crash boxes, the crash boxand the bumper beam will be the only parts that are damaged. The otherparts of the vehicle, that is, the panel 17 in FIG. 1, will not bedamaged.

What is claimed is:
 1. A bumper beam arrangement for a vehicle,comprising a bumper beam (11) that has an open profile with a top end(20) and two sides (21,22), wherein the beam is mounted on two crashboxes (12,13), which are mounted to the vehicle body and protrude intothe profile and are fastened to the top end (20) of the profile,characterised in that the crash boxes (12,13) taper off and protrudeinto the profile with their narrow ends so that the crash boxes forcethe sides of the profile (21,22) to widen the profile and make itflatter when the crash boxes are axially compressed.
 2. A bumper beamarrangement according to claim 1, characterised in that the beam (11)has a hat profile.